This invention relates generally to mechanisms for allowing selective engagement and disengagement between mechanical rotary elements and more particularly relates to such mechanisms which automatically disengage when one of the rotary elements is rotated by a power source above a predetermined speed.
When servicing many machines it is often necessary for operators to manually rotate shafts of the machines to adjust operational features of the machines. An example of this is found in buckle-type folders wherein buckle rolls must usually be hand rotated to adjust their "gaps" and "loads." In the prior art, easily-accessible handwheels have often been attached to shafts to enable operators to easily hand rotate the shafts. However, this structure has been found to be hazardous to operators in that the shafts, and the attached handwheels, often rotate at high speeds. Thus, when an operator inadvertently grabs or touches a rotating handwheel during operation of the machine, he can be severely injured. It is therefore an object of this invention to provide a mechanism which automatically disengages a handwheel from a shaft when the shaft is rotated above a predetermined speed.
It has been suggested to overcome the above-mentioned problem by providing a handwheel which is rotatively mounted on a stationary frame, but does not normally engage the shaft. In this respect, the handwheel is biased outwardly, away from engagement with the shaft, but can be depressed inwardly to engage the shaft. Thus, an operator can manually rotate the shaft by depressing the handwheel but when he releases the handwheel, the handwheel automatically disengages from the shaft so that the handwheel will not turn when the machine is operating. This handwheel mechanism has actually been found to have some features which are even more hazardous than the above-described handwheels that are attached directly to the shafts. In this respect, with a handwheel that can be selectively disengaged and engaged, an operator sometimes inadvertently engages the handwheel while its shaft is rapidly rotating, thereby causing a sudden rotation of the handwheel to the operator's injury. Thus, it is an object of this invention to provide a disengageable handwheel mechanism which cannot be inadvertently engaged with a shaft when the shaft is rotating above a predetermined speed.
Another difficulty with the above-described disengageable handwheel is that it does not remain engaged while adjustments are being made unless an operator maintains a depressing force on it. This feature is somewhat inconvenient for operators who are concentrating on the adjustment they are making and sometimes cannot continually maintain a depressing force. Thus, each time they wish to rotate a particular shaft, they must reengage its handwheel therewith. Therefore, it is yet another object of this invention to provide an automatic handwheel disengaging mechanism which allows a handwheel to remain engaged when it is released by an operator so long as the shaft is not rotated above a predetermined speed.
Finally, it is an object of this invention to provide a handwheel mechanism of the type described above which is uncomplicated and relatively easy to manufacture.